Increase in mental diseases, in particular depression, anxiety, autonomic imbalance and the like caused by excessive stress due to mental or physical pain has become a serious problem. Against such backdrop, many anti-depressants and anti-anxiety agents containing a chemical substance as active ingredient have been developed and used. Meanwhile, it is also known that conventional pharmaceutical drugs have problems of side effects, dependence and the like.
A safe ingredient originating from foods and having the function described above is desirable. Examples of foods and food ingredients that are known to have anti-depression effect and anti-anxiety effect include GABA, ginseng, St. Jone's wort, and Apocynum venetum extract. Examples of foods and food ingredients that are known to have anti-stress effect include theanine, soy bean peptide, cacao polyphenol, a matsutake mushroom and Grifola frondosa (Non-Patent Document 1). However, their effects are all moderate.    Non-Patent Document 1: Development and Prospects of Anti-stress Foods, Supervised by Hidehiko Yokogoshi, CMC Publishing CO., LTD (2006)